Method and device for transmitting and receiving packet in communication system

ABSTRACT

The present disclosure relates to a method and a device for transmitting and receiving a packet in a communication system. A method for transmitting a packet according to the present disclosure comprises the steps of: generating at least one source block including source packets for transmitting contents; performing forward error correction (FEC) encoding and generating at least one reconstructed block including reconstructed packets for restoring the source packets; and transmitting signaling information including packet identification information on the at least one source block and a packet stream including the source packets and the reconstructed packets, wherein header information of the reconstructed packets includes the number of source packets included in each source block according to the packet identification information, and information indicating the start numbers of the source packets included in the each source block.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 16/137,231, filed on Sep. 20, 2018, which was a continuationapplication of prior application Ser. No. 15/111,322, filed on Jul. 13,2016, which was issued as U.S. Pat. No. 10,153,863 on Dec. 11, 2018,which was the U.S. National Stage application under 35 U.S.C. § 371 ofan International application number PCT/KR2015/000358, filed on Jan. 13,2015 and was based on and claimed the priority under 35 U.S.C. § 119(a)of a Korean patent application number 10-2014-0004256, filed on Jan. 13,2014, and claimed the priority under 35 U.S.C. § 119(a) of a Koreanpatent application number 10-2014-0004259, filed on Jan. 13, 2014, andclaimed the priority under 35 U.S.C. § 119(a) of a Korean patentapplication number 10-2014-0083810, filed on Jul. 4, 2014, in the KoreanIntellectual Property Office, the disclosure of which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to packet transmitting/receiving methodsand devices in communication systems.

BACKGROUND ART

As various contents are diversified, and high-volume contents, such ashigh-definition (HD) contents, ultra-high-definition (UHD) contents,proliferate, data congestion increases. Under such circumstance,contents transmitted from a sensor (e.g., a Host A) are not normallytransferred to a receiver (e.g., a Host B), and some of the contents arelost on the route.

Generally, since data is transmitted in packet units, content lossoccurs in packet units. A packet includes one block of transmitted data(e.g., payload), address information (e.g., the sender's address anddestination address) and management information (e.g., header).Accordingly, in case packet loss occurs over the network, the receivercannot receive lost packets and cannot be thus aware of data andmanagement information in the lost packets. This causes userinconvenience in various types, such as degraded audio quality,deterioration of video quality or image distortion, subtitle missing, orfile loss. Thus, in order to restore data loss caused on a network,application layer forward error correction (AL-FEC) and method forconfiguring and transmitting/receiving FEC packets for the same areneeded.

DISCLOSURE Technical Problem

MPEG Output Document W13982 (ISO/IEC 23008-1 MPEP Media Transport (MMT))Final Draft International Specification Annex C defines AL-FEC Frameworkfor MMT. Repair packets are generated using an FEC code for sourcepackets for FEC protection are generated, and the source packets areFEC-protected and added with source FEC payload identifiers (IDs) togenerate FEC source packets, which are transmitted along with the repairpackets. The AL-FEC message containing the FEC-related configurationinformation is previously or periodically transmitted before the FECsource packets and repair packets are transmitted, allowing thereceiving terminal to be aware of the FEC-related configurationinformation.

The source packets are transmitted, added with the source FEC payloadIDs. Thus, in order to generate other repair packets for the same sourcepackets, other source FEC payload IDs need to be added. Thus, generatingseveral repair packets having different FEC configurations for onesource packet is limited or becomes inefficient.

Further, in case the transmitter sends only source packets without FECprotection, and an intermediate node in the network performs FECprotection, such problem arises that the network node is required to addsource FEC payload IDs to the source packets transmitted by thetransmitter. Thus, a need exists for a method for performing FECprotection without adding source FEC payload IDs to source packets.

Thus, according to the present disclosure, there are provided a methodand device for efficiently transmitting and receiving packets in acommunication system using FEC.

Further, according to the present disclosure, there are provided amethod and device for transmitting and receiving packets without addingsource FEC payload IDs to source packets using repair FEC payload IDstransmitted in AL-FEC messages and repair packets in a communicationsystem using FEC.

Technical Solution

According to an embodiment of the present disclosure, a method fortransmitting a packet in a communication system comprises the steps ofgenerating at least one source block including source packets fortransmission of a content, generating at least one repair blockincluding repair packets to restore the source packets by performingforward error correction (FEC) encoding, and transmitting a packetstream including the repair packets and the source packets and signalinginformation including packet identification information for the at leastone source block, wherein header information of the repair packetsincludes information indicating the number of source packets included ineach source block per packet identification information and a startnumber of the source packets included in each source block.

According to an embodiment of the present disclosure, a devicetransmitting a packet in a communication system comprises a transmittingunit transmitting the packet, an encoding unit performing forward errorcorrection (FEC) encoding, and a controller controlling the operationsof generating at least one source block including source packets fortransmission of a content, generating at least one repair blockincluding repair packets to restore the source packets by performingforward error correction (FEC) encoding, and transmitting a packetstream including the repair packets and the source packets and signalinginformation including packet identification information for the at leastone source block, wherein header information of the repair packetsincludes information indicating the number of source packets included ineach source block per packet identification information and a startnumber of the source packets included in each source block.

According to an embodiment of the present disclosure, a method fortransmitting a packet in a communication system includes a transmittingunit including the process of generating MMT packets for a signalingmessage (including an AL-FEC message) and Assets to be transmitted, theprocess of generating a repair symbol block by performing FEC encodingon an FEC configuration, such as an FEC coding structure, an SSBG mode,and an FEC code, defined in an AL-FEC message for the MMT packets, i.e.,source packets, corresponding to Assets to be FEC protected among theAssets, and the process of adding an FEC repair payload ID proposedherein to the repair symbol(s) to generate an FEC repair packet, and theprocess of transmitting the MMT packet, and FEC repair packet, alongwith the signaling message including the AL-FEC message, in an MMTpacket stream.

According to an embodiment of the present disclosure, higher-qualityservices may be offered to the user.

According to an embodiment of the present disclosure, the receivingdevice may differentiate each data stream from separate controlinformation different from the source packet or stream differentiatinginformation in the FEC packet, grasp the repair stream generated for FECprotection on each data stream, smoothly perform FEC decoding, andgenerate a repair flow for a predetermined number of data streamsincluded in the generated source packet flow without influencing thesource packet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are views illustrating a network topology and data flow;

FIG. 2 is a view illustrating a configuration of a MMT system accordingto an embodiment of the present disclosure;

FIG. 3 is a view illustrating a structure of a MMT package according toan embodiment of the present disclosure;

FIG. 4 is a view illustrating a configuration of configurationinformation included in a MMT package according to an embodiment of thepresent disclosure;

FIG. 5A is a view illustrating a source packet, source symbol, and FECrepair packet format according to an embodiment of the presentdisclosure;

FIGS. 5B and 5C are views illustrating the configuration of a sourcepayload, source symbol, and FEC repair packet format according to anembodiment of the present disclosure;

FIG. 6A is a view illustrating a method for configuring a source packetflow according to an embodiment of the present disclosure;

FIGS. 6B and 6C are views illustrating a method for configuring two FECsource packet flows from a source packet flow and generating one repairflow for each FEC source packet flow and examples of a MMT packet headerand FEC repair payload ID according to an embodiment of the presentdisclosure;

FIG. 7A is a view illustrating an operation of a transmitter for packetprotection according to an embodiment of the present disclosure;

FIG. 7B is a view illustrating an operation of a transmitter for payloadprotection according to an embodiment of the present disclosure;

FIG. 8A is a view illustrating an operation of a receiver for packetprotection according to an embodiment of the present disclosure;

FIG. 8B is a view illustrating an operation of a receiver for payloadprotection according to an embodiment of the present disclosure;

FIG. 9 is a flowchart illustrating an operation configuring a sourcesymbol block according to an embodiment of the present disclosure;

FIG. 10 is a view illustrating a dependent repair FEC payload IDaccording to an embodiment of the present disclosure;

FIG. 11A is a view illustrating a relation between an AL-FEC message andrepair FEC payload ID of a repair packet according to an embodiment ofthe present disclosure;

FIG. 11B is a view illustrating a method for setting fields of a repairFEC payload of a repair packet for a packet_ID included in a source flowbut excluded from some source packet block according to an embodiment ofthe present disclosure;

FIG. 12 is a view illustrating an example of a configuration of a repairFEC payload ID according to an embodiment of the present disclosure;

FIG. 13A is a view illustrating an operation of a transmitter for packetprotection according to another embodiment of the present disclosure;

FIG. 13B is a view illustrating an operation of a transmitter forpayload protection according to another embodiment of the presentdisclosure;

FIG. 14A is a view illustrating an operation of a receiver for packetprotection according to another embodiment of the present disclosure;

FIG. 14B is a view illustrating an operation of a receiver for payloadprotection according to another embodiment of the present disclosure;

FIG. 15 is a flowchart illustrating an operation configuring a sourcesymbol block according to another embodiment of the present disclosure;

FIG. 16 is a view illustrating a repair FEC payload ID according toanother embodiment of the present disclosure;

FIG. 17A is a view illustrating a relation between an independent repairFEC payload ID and dependent repair FEC payload ID according to anotherembodiment of the present disclosure;

FIG. 17B is a view illustrating a method for setting fields of a repairFEC payload of a repair packet for a packet_ID included in a source flowbut excluded from some source packet block according to anotherembodiment of the present disclosure; and

FIGS. 18 and 19 are views illustrating an FEC source or repair packetblock including an independent repair FEC payload ID and dependentrepair FEC payload ID according to another embodiment of the presentdisclosure.

MODE FOR CARRYING OUT THE INVENTION

When determined to make the subject matter of the present disclosureunclear, the detailed of the known functions or configurations may beskipped. The terms as used herein are defined considering the functionsin the present disclosure and may be replaced with other terms accordingto the intention or practice of the user or operator. Therefore, theterms should be defined based on the overall disclosure.

First, the terms used herein are summarized in Tables 1 to 3 below.

TABLE 1 Term Description access unit smallest media data entity to whichtiming information can be attributed asset any multimedia data entitythat is associated with a unique identifier and that is used forbuilding a multimedia presentation code rate ratio between the number ofsource symbols and the number of encoding symbols encoding symbol unitof data generated by the encoding process encoding symbol set ofencoding symbols block FEC code algorithm for encoding data such thatthe encoded data flow is resilient to data loss FEC encoded flow logicalset of flows that consists of an FEC source flow and one or moreassociated FEC repair flows FEC payload ID identifier that identifiesthe contents of a MMT packet with respect to the MMT FEC scheme FECrepair flow data flow carrying repair symbols to protect an FEC sourceflow FEC repair MMT packet along with repair FEC payload identifier topacket deliver one or more repair symbols of a repair symbol block FECsource flow flow of MMT packets protected by an MMT FEC scheme FECsource MMT packet along with source FEC payload identifier packet

TABLE 2 Term Description media fragment unit fragment of a mediaprocessing unit media processing generic container for independentlydecodable timed or non- unit timed data that is media codec agnostic MMTentity software and/or hardware implementation that is compliant to aprofile of MMT MMT FEC forward error correction procedure that definesthe additional scheme protocol aspects required to use an FEC scheme inMMT MMT packet formatted unit of the media data to be delivered usingthe MMT protocol. MMT payload formatted unit of media data to carry MMTpackages and/or signaling messages using either the MMT protocol or anInternet application layer transport protocols (e.g., RTP) MMT protocolapplication layer transport protocol for delivering MMT payload over IPnetworks MMT receiving MMT entity that receives and consumes media dataentity MMT sending MMT entity that sends media data to one or more MMTentity receiving entities

TABLE 3 Term Description non-timed data media data that do not haveinherent timeline for the decoding and/or presentation of its mediacontent package logical collection of media data, delivered using MMTrepair FEC FEC payload ID for repair packets payload ID repair symbolencoding symbol that contains redundancy information for errorcorrection repair symbol set of repair symbols which can be used torecover lost block source symbols source FEC FEC payload ID for sourcepackets. payload ID source packet segmented set of FEC source flow thatis to be protected block as a single block source symbol unit of data tobe encoded by an FEC encoding process source symbol set of sourcesymbols generated from a single source block packet block timed data anydata that has inherent timeline information for the decoding and/orpresentation of its media contents.

In an embodiment of the present disclosure, the header of the sourcepacket or FEC repair packet includes information for differentiating thesource packet or FEC repair packet. In case a packet transmission methodadding a separate source symbol ID (SS_ID) for letting the order ofsource symbols in the source symbol block known to the source packet andpacket transmission method according to the present disclosure are usedtogether, the header of the FEC repair packet or source packet accordingto the present disclosure includes at least one of informationindicating whether the packet is source packet+SD_ID or indicating thesource packet itself and information differentiating the FEC repairpackets according to the present disclosure.

The following Table 4 represents an embodiment of the FEC type of MMTpacket header and represents the value of FEC_type (or MMT packet type).

TABLE 4 Value Description 0 MMT packet without FEC Source Payload ID 1MMT packet with FEC Source Payload ID 2 MMT packet for repair symbol(s)for FEC Payload Mode 0 (FEC repair packet) 3 MMT packet for repairsymbol(s) for FEC Payload Mode 1 (FEC repair packet)

NOTE, If FEC type is set to 0, it indicates that FEC is not applied tothis MMT packet or that FEC is applied to this MMT packet without addingFEC Source Payload ID. In the latter case, the combination ofpacket_sequence_number and packet_id in this packet identify thelocation of this MMT packet within Source Packet Block which isidentified by the FEC repair payload ID of its associated FEC repairpacket (e.g. replacement of SS_ID).

Further, such information for differentiating packets has the PayloadID_Mode Flag indicating whether FEC applies and packets are transmittedin the legacy method through the AL_FEC message or FEC applies andtransmission is performed according to the present disclosure and it istransmitted to the receiving terminal.

Payload ID_Mode Flag=1, packet transmission method applying FECaccording to the present disclosure (that is, the information in thesource packet replaces SS_ID without using a separate SS_ID in thesource packet and follows the FEC repair packet format (e.g., FEC RepairPayload ID) according to the present disclosure).

Payload ID_Mode Flag=0, packet transmission method applying FEC as inthe conventional invention (that is, the source packet adds a separateSS_ID and follows the FEC repair packet format (e.g., repair FEC PayloadID) according to the conventional invention.)

Hereinafter, parity and repair are interchangeably used in the samemeaning.

First, the basic concept of an embodiment of the present disclosure isdescribed.

An Embodiment

A method for transmitting packets in a communication system according toan embodiment of the present disclosure is described. The transmittergenerates MMT packets for a signaling message (including e.g., AL-FECmessage) and Assets for transmission. The transmitter performs FECencoding on FEC configurations such as FEC coding structure, SSBG mode,and FEC code, defined in the AL-FEC message for the MMT packets, i.e.,source packets, corresponding to the Assets for FEC protection among theAssets, thereby generating a repair symbol block. The transmitter addsthe FEC repair payload ID according to the present disclosure to therepair symbol(s) to generate the FEC repair packet. The transmittertransmits the MMT packet and FEC repair packet, along with the Signalingmessage including the AL-FEC message, in a MMT packet stream. The AL-FECmessage may also be transmitted before transmitting the MMT packet orFEC repair packet.

Here, the repair FEC payload ID proposed herein includes at least oneof, e.g., M, T, SSM, timestamp, SS_start_seq_nr[0]˜[N−1], L[0]˜[N−1],SSB_length [0]˜[N−1], L2, RSB_length, and L3, RS_ID. The FEC repairpayload ID may be included in the header of the FEC repair packet.

Hereinafter, each information that may be included in the FEC repairpayload ID is described in detail.

“M” indicates whether the repair FEC payload ID of the repair packet isa dependent repair FEC payload ID or independent repair FEC payload ID(information necessary for FEC decoding processing may be obtained witha combination of Dependent repair FEC payload ID definition, i in therepair FEC payload ID, and information stored in the AL-FEC message).The Independent repair FEC payload ID indicates that informationnecessary for FEC decoding processing may be obtained with only theinformation of the packet including the Independent repair FEC payloadID without the information stored in the AL-FEC message. In case onlyDependent repair FEC Payload ID is used but the Independent repair FECPayload ID is not, the M field remains Reserved Field. The followinginformation denotes the meaning of each Field in the case being used asDependent repair FEC Payload ID.

“T” is flag information indicating whether there is timestamp field.

“SSM” is information indicating the size of SS_start_seq_nr field (e.g.,size of SS_start_seq_nr field(in bits)=8+8*SSM).

“timestamp” denotes the timestamp stored in the first source packet ofthe source packet block protected by the repair packet.

“SS_start_seq_nr[i]” denotes the LSB value as large a size as 8+8*SSMbits in the lowest packet_sequence_number among source packets of thesource packet (or symbol) block having the i^(th) packet_ID value in thesource flow described in the AL-FEC message (e.g., ifpacket_sequence_number is 32 bits, and 8+8*SSM is 24 bits, the remaining24 bits value except for the first 8 bits in the packet_sequence_number.Accordingly, it may be known which packet has the lowest source packet(i.e., the first or start source packet) among the source packets havingthe same packet ID (i.e., having the ith packet ID) in the source packet(or symbol) block through the “SS_start_seq_nr[i]”. In anotherembodiment, although the lowest sequence number is not used, otherinformation allowing it to be known which packet is the first or startsource packet in the source packet (or symbol) block may also beavailable. The packets belonging to different Assets may bedistinguished using the packet ID. For example, if the source packet ofAsset a is a packet for transmitting video data, and the source packetof Asset b is a packet for transferring audio data, the packet ID of theAsset a packet and the packet ID of the Asset b packet differ from eachother.

“L[i]” is information indicating the size of SSB_length[i] field and isgiven as SSB_length field size=6+8*L.

“SSB_length[i]” denotes the number (i=0, 1, . . . , N−1) of sourcepackets (or symbols) in the source packet (or symbol) block. The numberof source packets (or symbols) may be understood as the number of sourcepackets having the same packet ID (i.e., having the ith packet ID) inthe source packet (or symbol) block.

“L2” is information indicating the size of RSB_length field and is givenas, e.g., RSB_length field size=6+8*L2.

That is, as exemplified in FIG. 11A, information of SSB_length fields1103 and the SS_start_seq_nr field's 1101 included in the repair FECpayload ID of the repair packet denotes the start sequence number andthe number of source packets corresponding to the Packet_ID's 1105included in the Source Flow described in the AL-FEC message. Even incase the number of Packet_ID's included in the Source Flow is smallerthan the number of Packet_ID's included in the source packet (or symbol)block, as shown in FIG. 11B, the repair FEC payload ID of the repairpacket for the source packet (or symbol) block has SS_start_seq_nrfield's and SSB_length field's as many as the number of Packet_ID'sincluded in the Source flow described in the AL-FEC message which havethe same order. However, a particular value is set as SS_start_seq_nrfield or SSB_length field corresponding to the order of Packet_IDs notincluded in the source packet (or symbol) block, thereby indicating thatthe related source packet (or symbol) block does not include thePacket_ID. As an example, the SSB_length field value may be set to 0 toindicate that the packet having the Packet_ID is not included in thesource packet (or symbol) block.

Specifically, referring to FIG. 11B(a), in case whereas the source flowdescribed in the AL-FEC message consists of three Packet_ID's (0,1,2),source packet (or symbol) Block #1 consists of 0, 1, and 2 (1101),source packet (or symbol) block #2 of 0 and 1 (1103), and source packet(or symbol) block #3 of 1 and 2 (1105), as shown in FIG. 11B(b), therepair FEC payload ID of the repair packet for the source flow includesthree SS_start_seq_nr's and three SSB_length fields as in the order ofthe Packet_ID's 0, 1, and 2, but in its field value, the repair FECpayload ID of the repair packet for source packet (or symbol) block 1sets SS_start_seq_nr and SSB_length for packet_ID 0, 1, and 2, therepair FEC payload ID of the repair packet for source packet (or symbol)block2 sets SS_start_seq_nr and SSB_length for the packet_ID 0 and 1,and does not include packet_ID 2, and thus, sets 0 (1107, 1109) inSSB_length Field to indicate that the source packet (or symbol) block2does not include packet_ID 2. Since the source packet (or symbol) block3does not include Packet_ID 0, the repair FEC payload ID of the repairpacket for source packet (or symbol) block 3 sets 0 to the SSB_lengthField and SS_start_seq_nr and SSB_length for Packet_ID's 1 and 2.Further, in the SSB_length field corresponding to the Packet_ID notincluded in the source packet (or symbol) block, the L field todetermine the size is set to 0, minimizing the size of SSB_length field.

“RSB_length” is information on the number of repair symbols of therepair symbol block included in the repair packet.

“L3” is information indicating the size of RS_ID field and is given as,e.g., RS_ID field size=6+8*L2.

“RS_ID” denotes the position of the repair symbol(s) in the repairpacket in the repair symbol block including the repair packet (e.g., itdenotes what number of repair symbol it is).

According to an embodiment of the present disclosure, the transmittingdevice may include a transmitting unit, an encoding unit performing FECencoding, and a controller controlling the operations of generating MMTpackets for a signaling message (including AL-FEC message) and Assets tobe transmitted, generating a repair symbol block by performing FECencoding, through the encoding unit, on the FEC configurations, such asFEC coding structure, SSBG mode, and FEC code, defined in the AL-FECmessage for the MMT packets, i.e., source packets corresponding to theAssets to be FEC protected among the Assets and adding an FEC repairpayload ID proposed herein to generate FEC repair packets andtransmitting the same, along with the signaling message including theAL-FEC message, in an MMT packet stream through the transmitting unit.

Here, the repair FEC payload ID proposed herein includes at least one ofthe M, T, SSM, timestamp, SS_start_seq_nr[0]˜[N−1], L[0]˜[N−1],SSB_length [0]˜[N−1], L2, RSB_length, and L3, RS_ID.

Another transmission method according to an embodiment of the presentdisclosure is described. In generating and transmitting the MMT packetsfor the Signaling message and Assets to be transmitted, an intermediatenode in the network (e.g., Contribution Network) determines the Asset(s)and FEC configuration for FEC protection. The intermediate Nodegenerates the AL-FEC message including the Packet_ID list mapped to theAsset(s) based on the Asset(s) for FEC protection and FEC configurationinformation and repair flow ID mapped thereto and creates them into MMTpacket. The intermediate Node generates the repair symbol for FECprotection on the MMT packets corresponding to the Asset(s) to generatethe repair packets including the dependent repair FEC payload IDaccording to the present disclosure and transmits them. The networkintermediate Node may transmit the generated AL-FEC message beforetransmitting the source packet block.

Here, the repair FEC payload ID proposed herein includes at least one ofthe M, T, SSM, timestamp, SS_start_seq_nr[0]˜[N−1], L[0]˜[N−1],SSB_length [0]˜[N−1], L2, RSB_length, and L3, RS_ID. According to anembodiment of the present disclosure, another transmitting device isincluded in the intermediate Node of the network (e.g., ConfigurationNetwork). The transmitting device of the intermediate Node includes atransmitting unit, an encoding unit performing FEC encoding, and acontroller controlling the operations of determining the FECconfiguration information and Asset(s) for FEC protection in generatingand transmitting MMT packets for a signaling message and Assets to betransmitted, generating the AL-FEC message including the Packet_ID listmapped to the Asset(s) based on the Asset(s) for FEC protection and FECconfiguration information and repair flow ID mapped thereto and creatingthem into MMT packet, performing FEC encoding through the encoding unitfor FEC protection of the MMT packets corresponding to the Asset(s) togenerate repair symbols to generate the repair packets including thedependent repair FEC payload ID according to the present disclosure.Further, the controller controls the operation of transmitting the MMTpackets including the repair packet and the generated AL-FEC messagethrough the transmitting unit. Here, the repair FEC payload ID proposedherein includes at least one of the M, T, SSM, timestamp,SS_start_seq_nr[0]˜[N−1], L[0]˜[N−1], SSB_length [0]˜[N−1], L2,RSB_length, and L3, RS_ID. A receiving method according to an embodimentof the present disclosure is described. The transmitter receives thepacket including the AL-FEC message from the transmitter to obtain theAL-FEC message. The receiver obtains the packet ID list which is IDinformation for data streams included in the FEC source packet flow andthe mapping information on the repair flow ID protecting the packet IDlist from the AL-FEC message. The receiver determines whether the packetreceived from the transmitter is source packet or FEC repair packet. Incase the received packet is the FEC repair packet, the receiver obtainsrepair symbol from the FEC repair packet and obtains the Packet_ID listsof the source packets FEC protected by the Packet_ID of the FEC repairpacket (i.e., repair flow ID) from the received AL-FEC messageinformation. The receiver differentiates the source packets included inthe source packet block protected by the FEC repair packet from theSS_start_seq_nr list of the repair FEC payload ID of the FEC repairpacket and the Packet_ID list of the obtained source packets, configuresan encoding symbol block from the repair symbols and the source packetsdifferentiated from each other, and performs FEC decoding on theconfigured encoding symbol block to restore the source symbol, andobtains the source packets of the packet block lost during transmissionfrom the restored source symbol.

According to an embodiment of the present disclosure, a receiving devicemay include a receiving unit, a decoding unit performing FEC decoding,and a controller controlling the operations of receiving the packetincluding the AL-FEC message from the transmitter through the receivingunit to obtain the AL-FEC message, obtaining the packet ID list which isID information for data streams included in the FEC source packet flowand mapping information on the repair flow ID protecting the same fromthe AL-FEC message, differentiating whether the packet received from thetransmitter is the source packet or FEC repair packet, obtaining therepair symbol from the FEC repair packet, recognizing, from the obtainedAL-FEC message information, the Packet_ID lists of the source packetsFEC protected by the Packet_ID of the FEC repair packet (i.e., repairflow ID) to differentiate the source packets included in the sourcepacket block protected by the FEC repair packet from the SS_start_seq_nrlist of the repair FEC payload ID of the FEC repair packet and thePacket_ID list of the source packets, configuring an encoding symbolblock from the differentiated source packets and repair symbols,FEC-decoding the configured encoding symbol block through the decodingunit to restore the source symbol, and obtaining the source packet ofthe source packet block lost during the transmission from the restoredsource sb.

Hereinafter, embodiments of the present disclosure are described indetail with reference to the accompanying drawings.

FIGS. 1A and 1B are views illustrating a network topology and data flow.

Referring to FIG. 1A, the network topology includes a host A 102operating as a transmitter and a host B 108 operating as a receiver, andthe host A 102 and the host B 108 are connected through one or morerouters 104 and 106. The host A 102 and the host B 108 are connectedwith the routers 104 and 106 through Ethernet 118 and 122, and therouters 104 and 106 may be connected with each other via an optic fiber,satellite communication or other possible means 120. The data flowbetween the host A 102 and the host B 108 is performed through a linklayer 116, Internet layer 114, transport layer 112, and applicationlayer 110.

Referring to FIG. 1B, the application layer 130 generates data 130 to betransmitted through the AL-FEC. The data 130 may be the MMT packet dataas per MMT or RTP packet data obtained by splitting the compressed dataat the audio/video (AV) codec end using the real time protocol (RTP).The data 130 is converted into, e.g., a UDP packet 132 having a userdatagram protocol (UDP) header inserted therein, by the transport layer112. The Internet layer 114 generates the IP packet 134 by adding the IPheader to the UDP packet 132, and the link layer 116 adds the frameheader 136, and if necessary, frame footer, to the IP packet 134 toconfigure a frame 116 to be transmitted.

FIG. 2 is a view illustrating a configuration of a (MPEG MediaTransport) MMT system according to an embodiment of the presentdisclosure.

The left side of FIG. 2 shows the configuration of the MMT system, andthe right side shows the detailed structure of the delivery function.

The media coding layer 205 compresses the audio and/or video data andtransmits to the encapsulation function layer 210 (E. Layer).

The encapsulation function layer 210 packages the compressed audio/videodata into a format similar to the file format and transfers to thedelivery function layer 220.

The delivery function layer 220 (or “D. Layer”) formats the output ofthe encapsulation function layer 210 into an MMT payload and adds theMMT transmission packet header thereto and transfers to the transportprotocol layer 230 in the MMT transmission packet form. Or, the deliveryfunction layer 220 transfers the output of the encapsulation functionlayer 210 to the transport protocol layer 230 in the RTP packet formusing the legacy RTP protocol. Thereafter, the transport protocol layer230 converts into any one protocol of the user datagram protocol (UDP)and transmission control protocol (TCP) and transmits to the IP layer240. Finally, the IP layer 240 converts the output from the transportprotocol layer 230 into an IP packet and transmits it using the IPprotocol.

The present disclosure may protect MMTP packets, MMT payload, or payloaddata.

The control function layer 220 (C. Layer) manages the presentationsession and delivery session.

FIG. 3 is a view illustrating the structure of a MMT package.

As shown in FIG. 3, the MMT package 310 is transmitted/received with theclient 350 through the delivery function layer (D. Layer) 330-1 or 330-2of the network and includes MMT Assets 303-1 to 303-3, compositioninformation 301, and transport characteristics 305-1 and 305-2.

The MMT package 310 has functionality and operations for utilizingconfiguration information. The configuration information includes MMTAssets 303-1 to 303-2 list, composition information 301, and transportcharacteristics 305-1 and 305-2.

The description information describes the MMT package 310 and the MMTAssets 303-1 to 303-3. The composition information assists in consumingthe MMT Assets 303-1 to 303-3. The transport characteristics 305-1 and305-2 provide a hint for transfer of the MMT Assets 303-1 to 303-3.

The MMT package 310 describes the transport characteristic per MMTAsset. The transport characteristics 305-1 and 305-2 include errorresiliency information, and simple transport characteristic informationfor one MMT Asset may be lost or not. Further, the transportcharacteristics 305-1 and 305-2 may include quality of service (QoS),degree of acceptable loss, and degree of acceptable delay of each MMTAsset.

FIG. 4 is a view illustrating a configuration of configurationinformation included in a MMT package and its lower-level informationaccording to an embodiment of the present disclosure.

Referring to FIG. 4, the configuration information 401 includes theidentification information 403 on the package, information 405 on thelist of Assets which are components of the package, compositioninformation 407, transport characteristics 409, contents, and additionalinformation, and provide structural information, such as how and wherein the package such components are included. The known MMT standards maybe referenced for the detailed description of the configurationinformation included in the MMT package, and its detailed description isomitted.

FIG. 5A is a view illustrating a source packet, source symbol, and FECrepair packet according to an embodiment of the present disclosure.

Referring to FIG. 5A, Source Packet (=MMTP Packet) 501 includes MMTPacket Header, MMT Payload Header, and Payload (Data). Source Symbol 503is generated by adding Possibly Padding to Source Packet, and thePossibly Padding may be give through AL-FEC Message, as large Paddingdata (all 00h) as the difference from a predefined size of repair symbolmay be added. FEC Repair Packet 505 consists of repair symbols generatedfrom the source symbol block by MMT Packet Header, repair FEC PayloadID, and FEC encoding.

FIG. 5B is a view illustrating a source payload, source symbol, and FECrepair packet according to an embodiment of the present disclosure.

Referring to FIG. 5B, Source Payload (=MMT Payload) 511 includes MMTPayload Header and Payload (Data). Source Symbol 513 is generated byadding Possibly Padding to Source Payload 511, and the Possibly Paddingmay be give through AL-FEC Message, as large Padding data (all 00h) asthe difference from a predefined size of repair symbol may be added. FECRepair Packet 515 includes repair symbols generated from the sourcesymbol block by MMT Packet Header, FEC repair payload ID, and FECencoding.

FIG. 5C is a view illustrating a source payload, source symbol, and FECrepair packet according to an embodiment of the present disclosure.

Referring to FIG. 5C, Source Payload (=MMT Payload) 521 includes Payload(Data). Source Symbol 523 is generated by adding Possibly Padding toSource Payload 521, and the Possibly Padding may be give through AL-FECMessage, as large Padding data (all 00h) as the difference from apredefined size of repair symbol may be added. FEC Repair Packet 525includes repair symbols generated from the source symbol block by MMTPacket Header, FEC repair payload ID, and FEC encoding. The Repair FECPayload ID is given as shown in FIG. 10.

FIG. 10 is a view illustrating the dependent repair FEC payload IDaccording to an embodiment of the present disclosure, and the details ofeach information shown in FIG. 10 is shown in Table 5 below.

TABLE 5 Information Detail M (1 bit) indicates whether this repairpacket carries dependent repair FEC payload ID or independent repair FECpayload ID. It shall be set the same value on all of repair packets of arepair flow. When set to 1, it shall indicate that this packet carries adependent repair FEC payload ID and when set to 0, it shall indicatethat this packet carries an independent repair FEC payload ID. Ifindependent repair FEC payload ID is not used, then this field isreserved for future use. T (1 bit) indicates whether timestamp fieldpresent or not. When set to 0, timestamp field shall not be present andwhen set to 1, timestamp field shall present. SSM (2 bits) indicates thesize of the SS_start_seq_nr[i] field. The actual size of theSS_start_seq_nr[i] field is allocated to “8 + 8 * SSM” bits. RES (4bits) reserved for future use. timestamp (32 indicates the timestamp ofthe first packet of source packet bits) block which is protected by thisrepair packet. SS_start_seq_nr[i] indicates LSB part (8 + 8 * SSM bits)of the lowest (8 + 8 * SSM bits) packet_sequence_number of a packet withpacket_id[i] in the source symbol block which is protected by thisrepair packet. L[i] (2 bits) provides the number of additional words inthe SSB_length[i] field. SSB_length[i] indicates the number of packetswith ith packet_ID of (6 + 8 * L[i] bits) list_packet_ID field of thesource symbol block which is protected by this repair packet. L2 (2bits) provides the number of additional words in the RSB_length field.RSB_length the number of repair symbols generated in its associatedrepair (6 + 8 * L2 bits) symbol block. L3 (2 bits) provides the numberof additional words in the RS_ID field. RS_ID an integer number foridentifying the first repair symbol in the (6 + 8 * L2 bits) FEC repairpacket. It starts with 0 and is incremented by 1 with each repair symbolin its associated repair symbol block.

FIG. 6A is a view illustrating a method for generating a source packetflow according to an embodiment of the present disclosure.

Referring to FIG. 6A, when there are three Assets A, B, and C (601, 603,605) (e.g. non-timed data or timed data such as Audio data, Video data,txt, File as shown in FIG. 6A(a), each Asset is separated intopredetermined sizes of data, and is then added with MMT Payload Header,and MMT Packet Header to configure MMT Packet Flow (Source Packet Flow).As shown in FIG. 6A(b), each of Assets A, B, and C is separated intofive data payloads, and as shown in FIG. 6A(c), each is added with theheader including the Packet_ID 607 and Packet Sequence Number 609.Assignment is made as follows: Packet_ID=0 for identifying the packetsof Asset A, Packet_ID=1 for Asset B, and Packet_ID=2 for Asset C, andsuch assignment is made so that the Packet Sequence Number based on eachPacket_ID increases by one. An example of the header is the MMT packetheader.

FIGS. 6B and 6C are views illustrating an FEC source packet flow andmethod for generating a repair flow according thereto according to anembodiment of the present disclosure. In FIGS. 6B and 6C, referencedenotations H1 to H4 refer to their corresponding portions.

Referring to FIGS. 6B and 6C, from the source packet flow generated inFIG. 6A, FEC Source Packet Flow 1 consists of source packets generatedfrom Assets A and B to generate FEC Source Packet Block 1 (or SourceSymbol Block) (FIG. 6B(a)), and FEC Source Packet Flow 2 consists ofsource packets generated from Asset B and Asset C to generate FEC SourcePacket Block 2 (or Source Symbol Block) as shown in the drawings (FIG.6B(b)), and they respectively proceed with FEC encoding 611 and 613.From this, the FEC source packet block is converted into the sourcesymbol block by a method for the SSBG_MODE's and is subjected to FECencoding to generate FEC repair packets transmitting repair symbols.Although not shown, assuming that the location of the source packets inthe source packet block is determined by order of transmission whengenerating the source symbol block from the source packet block, thelocation of the source symbol corresponding to each source packet maydiffer in the source symbol block. The source symbols should be arrangedin the source symbol block based on the order of Packet_ID's specifiedin the repair FEC payload ID of repair packet. That is, in case thesource packet block consists of Assets A and B, although the sourcepackets for Asset A and Asset B are mixed in the source packet block,the source symbols for Asset A should be first arranged and the sourcesymbols for Asset B should be then arranged in the source symbol block,or they should be arranged in an opposite order, and then, thePacket_ID's mapped to the Assets fitting the order of arrangement andthe number of packet IDs included in the source packet block (or sourcesymbol block) are listed in the FEC repair payload ID of the FEC repairpacket. Otherwise, when the FEC source packet flow intended to beconfigured in the source packet flow as shown in FIGS. 6B and 6C isconfigured, and each source packet block (or source symbol block) isconfigured, the packets for Asset A are first arranged in the sourcepacket block (or source symbol block), and the packets for Asset B arearranged, and the Packet_ID's are listed based on the order or number ofPacket_ID's accordingly. Preferably, since the source packet flow is thestream of source packets based on actual order of transmission, thesource packets corresponding to the Packet_ID of the source packet firsttransmitted among the source packets for each source packet block arefirst arranged in the source packet block (or source symbol block), andthe source packets corresponding to the next Packet_ID are arranged.

FIGS. 7A and 7B are views illustrating the operation of a transmitterfor packet protection and payload protection according to an embodimentof the present disclosure. FIG. 7A illustrates the operation of thetransmitter for packet protection, and FIG. 7B illustrates the operationfor payload protection.

Referring to FIGS. 7A and 7B, first, the Data Stream 701 is transmittedvia Segmentation 703, Payloadization 705, and Packetization 707, to thepacket stream 711 by the transmitting unit 709. Taking MMT as anexample, an arrangement may be made so that Data Stream (701)=Asset.Segmentation 703 divides data in predetermined sizes. Payloadization 705adds header to the data, and the header stores information capable forreconfiguring the data from the packet received from the receiver. As anexample, MMT payload corresponds to this. Packetization 707 adds MMTpacket header to MMT Payload. The MMT Packet Header has Packet_ID andPacket Sequence Number and is thus utilized for FEC.

Further, in case Packet Protection is performed as shown in FIG. 7A, theMMT packets to be FEC protected are inputted to Source Symbol BlockGenerator 715 under the control of FEC Controller 713. Source SymbolBlock Generator 715 generates Source Symbol Block from MMT Packets(Source Packets) (refer to the example of FIG. 10), FEC encoder 717receives the Source Symbol Block to generate Repair Symbols, and eachRepair Symbol adds MMT Packet Header and FEC Repair Payload ID and it istransmitted in FEC Repair Packet. The repair FEC Payload ID may beconfigured as in Table 5 above according to the present disclosure.AL-FEC Message 719 passes through Payloadization 705, that is, adds MMTPayload Header, and then adds MMT Packet Header and it is transmitted ina packet separate from the data. Further, as shown in FIG. 7B, in casePayload protection is performed, it is the same as the Packet Protectionoperation described in connection with FIG. 7A except that MMT Payloador Payload data is inputted to Source Symbol Block Generator 721.

FIGS. 8A and 8B are views illustrating the operation of a receiver forpacket protection and payload protection. FIG. 8A illustrates theoperation of the receiver for packet protection, and FIG. 8B illustratesthe operation of the receiver for payload protection.

Referring to FIGS. 8A and 8B, the receiver, if receiving the PacketStream 801 through the Packet receiving unit 803, differentiates whetherthe received packet is the source packet or FEC repair packet. In caseseveral types of source packets (e.g., in case MMP packets (conventionalart) having a separate SS_ID and MMP packets with no such IDs (presentdisclosure) coexist) and several types of FEC repair packets (e.g., incase FEC repair packets according to the conventional art and FEC repairpackets according to the present disclosure coexist) coexist,information to differentiate the information is present in the MMTpacket header, and the receiver differentiates the packets based on theinformation. The differentiated packets are restored into the datastream 811 while passing De-packetization (e.g. MMT De-packetization orParse) 803, De-payloadization (MMT Payload Depayloadization or Parse)807, and De-segmentation 809.

Further, as shown in FIG. 8A, as an operation of the receiver in casepacket protection applies, the receiver grasps basic informationregarding the FEC configuration necessary for FEC decoding from theAL-FEC message 813. In case the received packet is the repair packet,the source packets protected by the repair packet from other informationthan number (or respective numbers) of Packet_ID's (# of Packet_IDs),List of Packet_IDs, List of SS_Start_Seq_Nrs, List of SSB_Length[ ]listed in the FEC repair payload ID and Packet_ID in the MMT packetheader and the repair symbols of the repair packet are recognized, andthe received Source Packet (MMT Packet) is inputted to Encoding SymbolGenerator 815 under the control of FEC Controller 819. Encoding SymbolGenerator 815 converts the source packet into source symbol according tothe SSBG mode given from the Source Packet, and it together with therepair symbols constitutes Encoding Symbol Block. FEC Decoder 817restores the lost source symbol using the repair symbols to obtain thesource packet. Then, source packet is transferred to De-packetization805.

Further, in case payload protection is applied as shown in FIG. 8B, thesame operation in light of information utilization of MMT Packet Headerand utilization of FEC Repair Payload ID information of FEC repairpacket as the packet protection operation of FIG. 8A applies except thatnot packet but payload is restored by Encoding Symbol Generator 821 andFEC Decoder 823.

FIG. 9 is a view illustrating an example of generating a source packetblock (or source symbol block) according to an embodiment of the presentdisclosure.

In the example shown in FIG. 9, from the flow of packets consisting ofthree Packet_ID's (FIG. 9(a)), packets corresponding to two Packet_ID'shaving packet_ID=0 or 1 are selected to configure FEC Source Packet Flow(=1 Source Packet Block) (FIG. 9(b)), and the packets having PacketID=0are first arranged, and then, packets having Packet_ID=1 are arranged togenerate the source symbol block (FIG. 9(c)). If the source packets havedifferent lengths upon conversion from Source Packet to Source Symbol,padding is needed (SSBG_MODE1), and if they are of the same length,padding is not required (SSBG_MODE0).

Hereinafter, a basic concept of another embodiment of the presentdisclosure is described.

Another Embodiment

A method for transmitting packets in a communication system according toanother embodiment of the present disclosure is described. Thetransmitter generates the MMT packet for signaling message and Assets tobe transmitted as set forth in MPEG output document w13982. Thetransmitter determines FEC configuration information such as the numberof Packet_ID's subjected to FEC protection, size of repair symbol to begenerated, window protection time, and FEC code to be applied to the MMTpacket corresponding to the Assets, i.e., source packets, subject to FECprotection among the Assets and performs FEC encoding to generate therepair symbol block as specified in w13982 as an example. Thetransmitter adds the repair FEC payload ID proposed herein to the repairsymbol(s) of the repair symbol block to generate and transmit the FECrepair packet.

Here, the repair FEC payload ID according to the present disclosureincludes at least one information of M, T, SSM, PM, C, W, timestamp,number (or respective numbers) of packet_ID's (# of packet_ID),packet_ID List, CP, PWT, RS_length, SS_start_seq_nr[0]˜[N−1],L[0]˜[N−1], SSB_length [0]˜[N−1], L2, RSB_length, L3, and RS_ID. The FECrepair payload ID may be included in the header of the FEC repairpacket.

Hereinafter, each information that may be included in the FEC repairpayload ID is described in detail.

“M” may obtain information necessary for FEC decoding processing in acombination of information indicating whether the repair FEC payload IDof repair packet is dependent repair FEC payload ID or independentrepair FEC payload ID (Dependent repair FEC payload ID definition,information stored in information different from the information inrepair FEC payload ID (e.g. AL-FEC message or Independent repair FECpayload ID). In an opposite concept, the Independent repair FEC payloadID indicates that information necessary for FEC decoding processing maybe obtained with only the information of the packet including theIndependent repair FEC payload ID without the information stored in theAL-FEC message.

“T” is flag information indicating whether there is timestamp field.

“SSM” is information indicating the size of SS_start_seq_nr field (e.g.,size of SS_start_seq_nr field (in bits)=8+8*SSM).

“PM” indicates whether the overall MMT flow is protected, one packet_IDis protected, two packet_ID's are protected, or three or morepacket_ID's are protected.

“C” indicates whether there is CP (Code Point) field, and “W” indicateswhether there is PWT (Protection Window Time) field.

“timestamp” denotes the timestamp stored in the first source packet ofthe source packet block protected by the repair packet.

The number (or respective numbers) of packet_ID's (# of packet_ID) fieldis a field present when the PM indicates that three or more Packet_ID'sare protected, and this indicates information on the number ofpacket_ID's.

“Packet_ID list” field lists the Packet_ID's and this is not providedwhen the PM indicates that the overall MMT flow is protected.

“CP (Code Point)” field is provided when C flag is on, and thisindicates the code point of the FEC code used to generate the repairpacket.

“PWT” is provided in case W flag is on and this indicates the FEC packetblock Window time constituted of the FEC source packet block and the FECrepair packet block in the repair flow including the repair packet (asan example, Protection Window Time as specified in W13982 may be used).

“RS_length” indicates the size information on repair symbol.

“SS_start_seq_nr[i]” denotes the LSB value as large a size as 8+8*SSMbits in the lowest packet sequence number among source packets of thesource packet block having the ith packet_ID value in the source flowdescribed in the AL-FEC message (e.g., if packet_sequence_number is 32bits, and 8+8*SSM is 24 bits, the remaining 24-bit value except for thefirst 8 bits in the packet_sequence_number. Accordingly, the startsequence number of the source packets of the source packet (or symbol)block may be known through “SS_start_seq_nr[i]”.

“L[i]” is information indicating the size of SSB_length[i] field and isgiven as SSB_length field size=6+8*L.

“SSB_length[i]” is the number (i=0, 1, . . . , N−1) of the sourcepackets of the source packet block having the ith packet_ID value in thesource flow specified in the AL-FEC message, and “L2” is informationindicating the size of RSB_length field and this is given as RSB_lengthfield size=6+8*L2.

“RSB_length” is information on the number of repair symbols of therepair symbol block included in the repair packet, L3 is informationindicating the size of RS_ID field and this is given as RS_ID fieldsize=6+8*L2, and “RS_ID” indicates the position of repair symbol(s) inthe repair packet in the repair symbol block including the repair packet(e.g., indicating what number of repair symbol it is).

According to an embodiment of the present disclosure, the transmittingdevice includes a controller generating the MMT packets for signalingmessage and Assets to be transmitted, e.g., as specified in MPEG outputdocument w13982, determining FEC configuration information such as thenumber of Packet_ID's subjected to FEC protection, size of repair symbolto be generated, window protection time, and FEC code to be applied tothe MMT packet corresponding to the Assets, i.e., source packets,subject to FEC protection among the Assets and performing FEC encodingto generate the repair symbol block as specified in w13982 and addingthe repair FEC payload ID proposed herein to the repair symbol(s) of therepair symbol block to generate and transmit the FEC repair packet.

Here, the repair FEC payload ID according to the present disclosureincludes at least one information of M, T, SSM, PM, C, W, timestamp, #of packet_ID, packet_ID List, CP, PWT, RS_length,SS_start_seq_nr[0]˜[N−1], L[0]˜[N−1], SSB_length [0]˜[N−1], L2,RSB_length, L3, and RS_ID.

Another transmission method according to an embodiment of the presentdisclosure is described. As specified in MPEG output document w13982, ingenerating and transmitting the MMT packets for the Signaling messageand Assets to be transmitted, an intermediate node in the network (e.g.,Contribution Network) determines the Asset(s) and FEC configuration forFEC protection. Further, the intermediate Node determines the Packet_IDlist mapped to the Asset(s) based on the Asset(s) for FEC protection andFEC configuration information and repair flow ID mapped thereto. Theintermediate Node generates the repair symbol block protecting the MMTpacket corresponding to the Asset(s), sets the repair flow ID value inthe Packet_ID in the repair symbol(s) of the generated repair symbolblock, adds the repair FEC payload ID according to the presentdisclosure to generate the FEC repair packet (MMT packet).

Here, the repair FEC payload ID according to the present disclosureincludes at least one of M, T, SSM, PM, C, W, timestamp, # of packet_ID,packet_ID List, CP, PWT, RS_length, SS_start_seq_nr[0]˜[N−1],L[0]˜[N−1], SSB_length [0]˜[N−1], L2, RSB_length, L3, and RS_ID.

According to an embodiment of the present disclosure, anothertransmitting device is included in the intermediate Node of the network(e.g., Configuration Network). The transmitting device of theintermediate Node includes a transmitting unit, an encoding unitperforming FEC encoding, and a controller controlling the operations ofdetermining the FEC configuration information and Asset(s) for FECprotection in generating and transmitting MMT packets for a signalingmessage and Assets to be transmitted, determining the Packet_ID listmapped to the Asset(s) based on the Asset(s) for FEC protection and FECconfiguration information and repair flow ID mapped thereto, performingFEC encoding through the encoding unit to generate the repair symbolblock protecting the MMT packet corresponding to the Asset(s), settingthe repair flow ID value in the Packet_ID in the repair symbol(s) of thegenerated repair symbol block, and adding the repair FEC payload IDaccording to the present disclosure to generate the FEC repair packet(MMT packet).

Here, the repair FEC payload ID according to the present disclosureincludes at least one of M, T, SSM, PM, C, W, timestamp, # of packet_ID,packet_ID List, CP, PWT, RS_length, SS_start_seq_nr[0]˜[N−1],L[0]˜[N−1], SSB_length [0]˜[N−1], L2, RSB_length, L3, and RS_ID. Areceiving method according to an embodiment of the present disclosure isdescribed. The receiver differentiates the received packet as to whetherit is the source packet or FEC repair packet. The receiver obtains therepair symbol from the FEC repair packet, recognizes, from the repairFEC payload ID of the FEC repair packet, the protection mode protectedby the FEC repair packet (i.e., whether the overall MMT flow isprotected, or one, two, or more Packet_ID's are protected), if theoverall MMT flow is protected, obtains the source packets based on theSSB_length information and the SS_start_seq_nr's of the repair FECpayload ID and the packet_count field of the received source packet, orunless the overall MMT flow is protected, obtains the source packetcorresponding to the source packet block from the received packet basedon the number of Packet_ID's protected, Packet_ID list, SS_start_seq_nr,and SSB_length from the repair FEC payload ID information to configurethe encoding symbol block, along with the repair symbols. The receiverperforms FEC decoding on the configured encoding symbol block andobtains the source packet of the source packet block lost duringtransmission from the restored source symbol.

According to an embodiment of the present disclosure, the receiver mayinclude a receiving unit, a decoding unit performing FEC decoding, and acontroller controlling the operations of differentiating whether thepacket received from the transmitter by the receiving unit is the sourcepacket or FEC repair packet, obtaining the repair symbol from the FECrepair packet, recognizes, from the repair FEC payload ID of the FECrepair packet, the protection mode protected by the FEC repair packet(i.e., whether the overall MMT flow is protected, or one, two, or morePacket_ID's are protected), if the overall MMT flow is protected,obtains the source packets based on the SSB_length information and theSS_start_seq_nr's of the repair FEC payload ID and the packet_countfield of the received source packet, or unless the overall MMT flow isprotected, obtaining the source packet corresponding to the sourcepacket block from the received packet based on the number of Packet_ID'sprotected, Packet_ID list, SS_start_seq_nr, and SSB_length from therepair FEC payload ID information to configure the encoding symbolblock, along with the repair symbols, performing FEC decoding on theconfigured encoding symbol block through the decoding unit to restorethe source symbol, and obtaining the source packet of the source packetblock lost during transmission from the restored source symbol.

A transmitting method according to another embodiment of the presentdisclosure is described. The transmitter generates the MMT packet forsignaling message and Assets to be transmitted as set forth in MPEGoutput document w13982. The transmitter determines FEC configurationinformation such as the number of Packet_ID's subjected to FECprotection, size of repair symbol to be generated, window protectiontime, and FEC code to be applied to the MMT packet corresponding to theAssets, i.e., source packets, subject to FEC protection among theAssets. The transmitter includes the independent repair FEC payload IDin at least one repair packet of the repair packets protecting thesource packet block in performing FEC encoding to generate the repairsymbol block as specified in w13982 and adding the repair FEC payload IDproposed herein to the repair symbol(s) of the repair symbol block togenerate and transmit the FEC repair packet.

According to an embodiment of the present disclosure, the transmittingdevice includes a transmitting unit, an encoding unit performing FECencoding, and a controller controlling the operations of generating theMMT packets for signaling message and Assets to be transmitted, e.g., asspecified in MPEG output document w13982, determining FEC configurationinformation such as the number of Packet_ID's subjected to FECprotection, size of repair symbol to be generated, window protectiontime, and FEC code to be applied to the MMT packet corresponding to theAssets, i.e., source packets, subject to FEC protection among the Assetsand including the independent repair FEC payload ID in at least onerepair packet of the repair packets protecting the source packet blockin performing FEC encoding to generate the repair symbol block asspecified in w13982 and adding the repair FEC payload ID proposed hereinto the repair symbol(s) of the repair symbol block to generate andtransmit the FEC repair packet.

Another transmission method according to an embodiment of the presentdisclosure is described. As specified in MPEG output document w13982, ingenerating and transmitting the MMT packets for the Signaling messageand Assets to be transmitted, an intermediate node in the network (e.g.,Contribution Network) determines the Asset(s) and FEC configuration forFEC protection. The intermediate Node determines the Packet_ID listmapped to the Asset(s) based on the Asset(s) for FEC protection and FECconfiguration information and repair flow ID mapped thereto andgenerates the repair symbol block protecting the MMT packetcorresponding to the Asset(s). The intermediate Node includes andtransmits the independent repair FEC payload ID in at least one repairpacket among the repair packets protecting the source packet block insetting the repair flow ID value in the Packet_ID in the repairsymbol(s) of the generated repair symbol block and adding the repair FECpayload ID according to the present disclosure to generate the FECrepair packet (MMT packet).

According to an embodiment of the present disclosure, anothertransmitting device is included in the intermediate Node of the network(e.g., Configuration Network). The transmitting device of theintermediate Node includes a transmitting unit, an encoding unitperforming FEC encoding, and a controller controlling the operations ofdetermining the FEC configuration information and Asset(s) for FECprotection in generating and transmitting MMT packets for a signalingmessage and Assets to be transmitted, determining the Packet_ID listmapped to the Asset(s) based on the Asset(s) for FEC protection and FECconfiguration information and repair flow ID mapped thereto, performingFEC encoding through the encoding unit to generate the repair symbolblock protecting the MMT packet corresponding to the Asset(s), andincluding and transmitting the independent repair FEC payload ID in atleast one repair packet of the repair packets protecting the sourcepacket block in setting the repair flow ID value in the Packet_ID in therepair symbol(s) of the generated repair symbol block, and adding therepair FEC payload ID according to the present disclosure to generatethe FEC repair packet (MMT packet).

A receiving method according to an embodiment of the present disclosureis described. The receiver differentiates whether the packet receivedfrom the transmitter is the source packet or FEC repair packet andobtains at least one independent repair FEC payload ID from the FECrepair packet to obtain the repair symbol. The receiver recognizes, fromthe repair FEC payload ID of the FEC repair packet, the protection modeprotected by the FEC repair packet (i.e., whether the overall MMT flowis protected, or one, two, or more Packet_ID's are protected), if theoverall MMT flow is protected, obtains the source packets based on theSSB_length information and the SS_start_seq_nr's of the repair FECpayload ID and the packet_count field of the received source packet, orunless the overall MMT flow is protected, obtains the source packetcorresponding to the source packet block from the received packet basedon the number of Packet_ID's protected, ssbg_mode, Packet_ID list,SS_start_seq_nr, and SSB_length from the repair FEC payload IDinformation to configure the encoding symbol block, along with therepair symbols. The receiver performs FEC decoding on the configuredencoding symbol block and obtains the source packet of the source packetblock lost during transmission from the restored source symbol.

According to an embodiment of the present disclosure, the receiver mayinclude a receiving unit, a decoding unit performing FEC decoding, and acontroller controlling the operations of differentiating whether thepacket received from the transmitter by the receiving unit is the sourcepacket or FEC repair packet and obtaining at least one independentrepair FEC payload ID from the FEC repair packet, obtaining the repairsymbol, recognizes, from the repair FEC payload ID of the FEC repairpacket, the protection mode protected by the FEC repair packet (i.e.,whether the overall MMT flow is protected, or one, two, or morePacket_ID's are protected), if the overall MMT flow is protected,obtains the source packets based on the SSB_length information and theSS_start_seq_nr's of the repair FEC payload ID and the packet_countfield of the received source packet, or unless the overall MMT flow isprotected, obtaining the source packet corresponding to the sourcepacket block from the received packet based on the number of Packet_ID'sprotected, ssbg_mode, Packet_ID list, SS_start_seq_nr, and SSB_lengthfrom the repair FEC payload ID information to configure the encodingsymbol block, along with the repair symbols, performing FEC decoding onthe configured encoding symbol block through the decoding unit torestore the source symbol, and obtaining the source packet of the sourcepacket block lost during transmission from the restored source symbol.

The header of the source packet or FEC repair packet includesinformation for differentiating the source packet or FEC repair packet.In case a packet transmission method adding a separate source symbol ID(SS_ID) for letting the order of source symbols in the source symbolblock known to the source packet and packet transmission methodaccording to the present disclosure are used together, the header of theFEC repair packet or source packet according to the present disclosureincludes at least one of information differentiating whether

-   -   Source Packet+SS_ID;    -   Source Packet itself (present disclosure);    -   FEC Repair Packet according to the conventional invention; and    -   FEC repair packet according to the present disclosure.

The following Table 6 represents an embodiment of the FEC type of MMTpacket header.

TABLE 6 Value Description 0 MMT packet without FEC Source Payload ID 1MMT packet with FEC Source Payload ID 2 MMT packet for repair symbol(s)for FEC Payload Mode 0 (FEC repair packet) 3 MMT packet for repairsymbol for FEC Payload Mode 1 (FEC repair packet)

NOTE, If FEC type is set to 0, it indicates that FEC is not applied tothis MMT packet or that FEC is applied to this MMT packet without addingFEC Source Payload ID.

Further, such information for differentiating packets has the PayloadID_Mode Flag indicating whether FEC applies and packets are transmittedin the legacy method through the AL_FEC message or FEC applies andtransmission is performed according to the present disclosure and it istransmitted to the receiving terminal.

Payload ID_Mode Flag=1, packet transmission method applying FECaccording to the present disclosure (that is, without using a separateSS_ID in the source packet, follows the FEC repair packet format(particularly, repair FEC Payload ID). In this case, use of theinformation (e.g., sequence number of source packet) in the sourcepacket allows the order of the source packets (or symbols) having thesame packet ID in the source packet (or symbol) block to be identifiedas if it is done by using SS_ID.

Payload ID_Mode Flag=0, packet transmission method applying FEC as inthe conventional invention (that is, the source packet adds a separateSS_ID and follows the FEC repair packet format (particularly, repair FECPayload ID) according to the conventional invention.)

Hereinafter, other embodiments of the present disclosure are describedwith respect to the drawings.

The features of the present disclosure described above in the aboveembodiments may be selectively applied to other embodiments of thepresent disclosure.

FIG. 12 is a view illustrating an example of a configuration of a repairFEC payload ID according to an embodiment of the present disclosure.

The details of each information shown in FIG. 12 are shown in Tables 7to 9 below.

TABLE 7 information Detail M (1 bit) indicates whether this repairpacket carries dependent repair FEC payload ID or independent repair FECpayload ID. When set to 1, it shall indicate that this packet carries adependent repair FEC payload ID and when set to 0, it shall indicatethat this packet carries an independent repair FEC payload ID. T (1 bit)indicates whether timestamp field present or not. When set to 0,timestamp field shall not be present and when set to 1, timestamp fieldshall present. SSM (2 bits) indicates the size of the SS_start_seq_nr[i]field. The actual size of the SS_start_seq_nr[i] field is allocated to“8 + 8 * SSM” bits. PM (2 bits) defines a source flow to be protected.The same value shall be set to this field of all repair packets for arepair flow. C (1 bit) indicates whether Code Point field present ornot. When set to 0, Code Point field shall not be present andpre-determined Code Point is used. When set to 1, Code Point field shallbe present. W (1 bit) indicates whether Protection Window Time fieldpresent or not. When set to 0, Protection Window Time field shall not bepresent. When set to 1, Protection Window Time field shall be present.timestamp indicates the timestamp of the first packet of source packet(32 bits) block which is protected by this repair packet. # of packet_idindicates the number of packet_ids which consists of a source (6 bits)flow to be protected. This field shall only present when PM set to 3.The same value shall be set to this field of all repair packets for arepair flow.

TABLE 8 information Detail ssbg_mode (2 bits) indicates the appliedsource symbol block generation mode to the source packet block which isprotected by this repair packet. list_packet_id provides list ofpacket_ID to be protected by a repair flow for (Num * 16 bits) thispacket. When PM set to 0, then this field shall not present, when PM setto 1 or 2 then Num = 1 or 2, respectively and when PM set to 3, Num = #of packet_id. The same value shall be set to this field of all repairpackets for a repair flow. CP (8 bits) indicates the Code Point which isused to generate the repair flow. This field shall only present when Cset to 1. The same value shall be set to this field of all repairpackets for a repair flow. PWT (32 bits) indicates Protection WindowTime of FEC source or repair packet block which is relevant to thisrepair packet. This field shall only present when W set to 1. The samevalue shall be set to this field of all repair packets for a repairflow. RS_length indicates the length (in bytes) of repair symbol. Thesame (16 bits) value shall be set to this field of all repair packetsfor a repair flow. SS_start_seq_nr[i] If PM set to 0, it indicates LSBpart (8 + 8 * SSM bits) of the (8 + 8 * SSM bits) lowest packet_count ofa packet in the source symbol block which is protected by this repairpacket. Otherwise, it indicates LSB part (8 + 8 * SSM bits) of thelowest packet_sequence_number of a packet with the ith packet_ID oflist_packet_ID field in the source symbol block which is protected bythis repair packet (i = 0, 1, . . . , Num − 1).

TABLE 9 information Detail L[i] (2 bits) provides the number ofadditional words in the SSB_length[i] field. SSB_length[i] indicates thenumber of packets with ith packet_ID of (6 + 8 * L[i] bits)list_packet_ID field of the source symbol block which is protected bythis repair packet. L2 (2 bits) provides the number of additional wordsin the RSB_length field. RSB_length the number of repair symbolsgenerated in its (6 + 8 * L2 bits)- associated repair symbol block. L3(2 bits) provides the number of additional words in the RS_ID field.RS_ID an integer number for identifying the first repair (6 + 8 * L2bits) symbol in the FEC repair packet. It starts with 0 and isincremented by 1 with each repair symbol in its associated repair symbolblock.

Note, if the field M indicates that this repair packet carries dependentrepair FEC payload ID, then PM, C and W fields are reserved.

2) If the field M indicates that this repair packet carries dependentrepair FEC payload ID, then # of packet_id, list_packet_id, CP, PWT andRS_length fields shall not be present.

The protection mode of the source flow protected in the “PM” field ofTable 7 above may be defined as in Table 10, for example.

TABLE 10 Value Description 0 Whole MMT flow is protected. (packet_countfiled in MMT packet headers shall be present) 1 A source flow, whichconsists of one packet_id, is protected. 2 A source flow, which consistsof two packet_ids, is protected. 3 A source flow, which consists of morethan two packet_ids, is protected.

FIG. 17A is a view illustrating a relation between an independent repairFEC payload ID and dependent repair FEC payload ID according to anotherembodiment of the present disclosure, and FIG. 17B is a viewillustrating a method for setting fields of a repair FEC payload of arepair packet for a packet_ID included in a source flow but excludedfrom some source packet block according to another embodiment of thepresent disclosure.

First, as shown in FIG. 17A, the number of SS_start_seq_nr fields andSSB_length fields are specified for all repair packets of the repairflow for the source flow based on the order and number of thePacket_ID's for the source flow specified in the Independent repair FECpayload ID. Even in case the number of Packet_ID's included in theSource Flow is smaller than the number of Packet_ID's included in thesource packet (or symbol) block, as shown in FIG. 17B, the repair FECpayload ID of the repair packet for the source packet (or symbol) blockhas SS_start_seq_nr field's and SSB_length field's as many as the numberof Packet_ID's included in the Source flow described in the independentFEC payload ID. However, a particular value is set as SS_start_seq_nrfield or SSB_length field corresponding to the order of Packet_IDs notincluded in the source packet (or symbol) block, thereby indicating thatthe related source packet (or symbol) block does not include thePacket_ID. As an example, the SSB_length field value may be set to 0 toindicate that the packet having the Packet_ID is not included in thesource packet (or symbol) block.

Specifically, referring to FIG. 17B(a), in case whereas the source flowdescribed in the AL-FEC message consists of three Packet_ID's (0,1,2),source packet (or symbol) Block #1 consists of 0, 1, and 2 (1701),source packet (or symbol) block #2 of 0 and 1 (1703), and source packet(or symbol) block #3 of 1 and 2(1705), as shown in FIG. 17B(b), therepair FEC payload ID of the repair packet for the source flow includesthree SS_start_seq_nr's and three SSB_length fields as in the order ofthe Packet_ID's 0, 1, and 2, but in its field value, the repair FECpayload ID of the repair packet for source packet (or symbol) block 1sets SS_start_seq_nr and SSB_length for packet_ID 0, 1, and 2, therepair FEC payload ID of the repair packet for source packet (or symbol)block2 sets SS_start_seq_nr and SSB_length for the packet_ID 0 and 1,and does not include packet_ID 2, and thus, sets 0(1707, 1709) inSSB_length Field to indicate that the source packet (or symbol) block2does not include packet_ID 2. Further, since the source packet (orsymbol) block3 does not include Packet_ID 0, the repair FEC payload IDof the repair packet for source packet (or symbol) block 3 sets 0 to theSSB_length Field and SS_start_seq_nr and SSB_length for Packet_ID's 1and 2. Further, in the SSB_length field corresponding to the Packet_IDnot included in the source packet (or symbol) block, the L field todetermine the size is set to 0, minimizing the size of SSB_length field.Meanwhile, the method for generating the source packet flow according toanother embodiment of the present disclosure is the same as thatdescribed above in connection with FIG. 6A.

In other words, when there are three Assets A, B, and C (e.g. non-timeddata or timed data such as Audio data, Video data, txt, File, each Assetis separated into predetermined sizes of data, and is then added withMMT Payload Header, and MMT Packet Header to configure MMT Packet Flow(Source Packet Flow). Each of Assets A, B, and C is split into five datapayloads and each adds the header including the Packet_ID and PacketSequence Number. Assignment is made as follows: Packet_ID=0 foridentifying the packets of Asset A, Packet_ID=1 for Asset B, andPacket_ID=2 for Asset C, and such assignment is made so that the PacketSequence Number based on each Packet_ID increases by one. An example ofthe header is the MMT packet header.

FIGS. 13A and 13B are views illustrating the operation of a transmitterfor packet protection and payload protection according to an embodimentof the present disclosure. FIG. 13A illustrates the operation of thetransmitter for packet protection, and FIG. 13B illustrates theoperation for payload protection.

Referring to FIGS. 13A and 13B, first, the Data Stream 1301 istransmitted via Segmentation 1303, Payloadization 1305, andPacketization 1307, to the packet stream 1311 by the transmitting unit1309. Taking MMT as an example, an arrangement may be made so that DataStream=Asset. Segmentation splits data into predetermined sizes.Payloadization adds header to the data, and the header storesinformation capable for reconfiguring the data from the packet receivedfrom the receiver. As an example, MMT payload corresponds to this.Packetization 1307 adds MMT packet header to MMT Payload. The MMT PacketHeader has Packet_ID and Packet Sequence Number and is thus utilized forFEC.

Further, in case Packet Protection is performed as shown in FIG. 13A,the MMT packets to be FEC protected are inputted to Source Symbol BlockGenerator 1315 under the control of FEC Controller 1313. Source SymbolBlock Generator 1315 generates Source Symbol Block from MMT Packets(Source Packets) (refer to the example of FIG. 10), FEC encoder 1317receives the Source Symbol Block to generate Repair Symbols, and eachRepair Symbol adds MMT Packet Header and FEC Repair Payload ID and it istransmitted in FEC Repair Packet. As set forth above, according toanother embodiment of the present disclosure, repair FEC payload ID maybe configured as shown in FIG. 12.

Further, as shown in FIG. 13B, in case Payload protection is performed,it is the same as the Packet Protection operation described inconnection with FIG. 13A except that MMT Payload or Payload data isinputted to Source Symbol Block Generator 1321.

In case the method according to the present disclosure and theconventional method both use the AL-FEC application scheme, theconventional method requires the AL-FEC message 1319 for AL-FEC decodingof the AL-FEC-applied packets, and in this case, the AL-FEC message 1319adds the MMT payload header by way of Payloadization 1305 and then addsMMT packet header and this is transmitted in a separate packet differentthe data. However, in case AL-FEC applies to only the method accordingto the present disclosure to perform transmission, the AL-FEC message1319 need not be transmitted in a separate packet. This is why theinformation required for FEC operation of the receiver according to thepresent disclosure is transmitted in the repair packet.

FIGS. 14A and 14B are views illustrating the operation of a receiver forpacket protection and payload protection. FIG. 14A illustrates theoperation of the receiver for packet protection, and FIG. 14Billustrates the operation of the receiver for payload protection.

Referring to FIGS. 14A and 14B, the receiver, if receiving the PacketStream 1401 through the Packet receiving unit 1403, differentiateswhether the received packet is the source packet or FEC repair packet.In case several types of source packets (e.g., in case MMP packets(conventional art) having a separate SS_ID and MMP packets with no suchIDs (present disclosure) coexist) and several types of FEC repairpackets (e.g., in case FEC repair packets according to the conventionalart and FEC repair packets according to the present disclosure coexist)coexist, information to differentiate the information is present in theMMT packet header, and the receiver differentiates the packets based onthe information. The differentiated packets are restored into the datastream 1411 while passing De-packetization (e.g., MMT De-packetizationor Parse) 1405, De-payloadization (MMT Payload Depayloadization orParse) 1407, and De-segmentation 1409.

As an operation in case the packet protection as shown in FIG. 14A isapplied, the receiver differentiates whether the received packet is thesource packet or repair packet, and in case the received packet is therepair packet, if the M field of the repair FEC payload ID of the repairpacket indicates the independent repair FEC payload ID, recognizes thesource packets protected by the repair packet from other informationthan number (or respective numbers) of Packet_ID's (# of Packet_IDs),List of Packet_IDs, List of SS_Start_Seq_Nrs, List of SSB_Length[ ]listed in the FEC repair payload ID and Packet_ID in the MMT packetheader and the repair symbols of the repair packet are recognized, andthe received Source Packet (MMT Packet) is inputted to Encoding SymbolGenerator 1415 under the control of FEC Controller 1419. Encoding SymbolGenerator converts the source packet into source symbol according to theSSBG mode given from the Source Packet, and it together with the repairsymbols constitutes Encoding Symbol Block. FEC Decoder 1417 restores thelost source symbol using the repair symbols to obtain the source packet,and the source packet is transferred to the De-packetization block 1405.

Further, in case payload protection is applied as shown in FIG. 14B, thesame operation in light of information utilization of MMT Packet Headerand utilization of FEC Repair Payload ID information of FEC repairpacket as the packet protection operation of FIG. 14A applies exceptthat not packet but payload is restored by Encoding Symbol Generator1421 and FEC Decoder 1423.

FIG. 15 is a view illustrating an example of generating a source packetblock (or source symbol block) according to an embodiment of the presentdisclosure.

Referring to FIG. 15, from the flow of packets consisting of threePacket_ID's (FIG. 15(a)), packets corresponding to two Packet_ID'shaving packet_ID=0 or 1 are selected to configure FEC Source Packet Flow(=1 Source Packet Block) (FIG. 15(b)), and the packets having PacketID=0are first arranged, and then, packets having Packet_ID=1 are arranged togenerate the source symbol block (FIG. 9(c)). If the source packets havedifferent lengths upon conversion from Source Packet to Source Symbol,padding is needed (SSBG_MODE1), and if they are of the same length,padding is not required (SSBG_MODE0).

FIG. 16 is a view illustrating a repair FEC payload ID according toanother embodiment of the present disclosure. The details of eachinformation shown in FIG. 16 are shown in Tables 11 to 13 below.

TABLE 11 information Detail M (1 bit) indicates whether this repairpacket carries dependent repair FEC payload ID or independent repair FECpayload ID. When set to 1, it shall indicate that this packet carries adependent repair FEC payload ID and when set to 0, it shall indicatethat this packet carries an independent repair FEC payload ID. T (1 bit)indicates whether timestamp field present or not. When set to 0,timestamp field shall not be present and when set to 1, timestamp fieldshall present. SSM (2 bits) indicates the size of the SS_start_seq_nr[i]field. The actual size of the SS_start_seq_nr[i] field is allocated to“8 + 8 * SSM” bits. I (1 bit) defines whether length repair datapresents in this FEC repair packet or not. If set to 1, length repairdata shall be present. Otherwise, length repair data shall not bepresent. C (1 bit) indicates whether Code Point field present or not.When set to 0, Code Point field shall not be present and pre-determinedCode Point is used. When set to 1, Code Point field shall be present. W(1 bit) indicates whether Protection Window Time field present or not.When set to 0, Protection Window Time field shall not be present. Whenset to 1, Protection Window Time field shall be present. timestampindicates the timestamp of the first packet of source packet (32 bits)block which is protected by this repair packet. ssbg_mode (2 bits)indicates the applied source symbol block generation mode to the sourcepacket block which is protected by this repair packet. The same valueshall be set to this field of all repair packets for a repair flow.

TABLE 12 information Detail # of packet_id indicates the number ofpacket_ids which consists of a source (6 bits) flow to be protected. Ifwhole MMT flow is protected, this field shall be set to 0. The samevalue shall be set to this field of all repair packets for a repairflow. list_packet_id provides list of packet_ID to be protected by arepair flow for (Num * 16 bits) this packet. When # of packet_id set to0, then this field shall not present, otherwise Num = # of packet_id.The same value shall be set to this field of all repair packets for arepair flow. CP (8 bits) indicates the Code Point which is used togenerate the repair flow. This field shall only present when C set to 1.The same value shall be set to this field of all repair packets for arepair flow. PWT (32 bits) indicates Protection Window Time of FECsource or repair packet block which is relevant to this repair packet.This field shall only present when W set to 1. The same value shall beset to this field of all repair packets for a repair flow. RS_lengthindicates the length (in bytes) of repair symbol. The same (16 bits)value shall be set to this field of all repair packets for a repairflow. SS_start_seq_nr[i] If PM set to 0, it indicates LSB part (8 + 8 *SSM bits) of the (8 + 8 * SSM bits) lowest packet_count of a packet inthe source symbol block which is protected by this repair packet.Otherwise, it indicates LSB part (8 + 8 * SSM bits) of the lowestpacket_sequence_number of a packet with the ith packet_ID oflist_packet_ID field in the source symbol block which is protected bythis repair packet (i = 0, 1, Num − 1). L[i] (2 bits) provides thenumber of additional words in the SSB_length[i] field.

TABLE 13 information Detail SPB_length[i] indicates the number ofpackets with ith packet_ID of (6 + 8 * L[i] bits) list_packet_ID fieldof the source symbol block which is protected by this repair packet. L2(2 bits) provides the number of additional words in the RSB_lengthfield. RSB_length the number of repair symbols in its associated repairsymbol (6 + 8 * L2 bits) block. L3 (2 bits) provides the number ofadditional words in the LRSB_length field. LRSB_length indicates thenumber of length repair data in its associated (6 + 8 * L3 bits) lengthrepair data block. This field only presents when length repair datapresents in this FEC repair packet. i.e., I is set to 1 L4 (2 bits)provides the number of additional words in the SSB_length field.SSB_length indicates the number of source symbols in the source symbol(6 + 8 * L4 bits) block. This field only presents when SSBG Mode 2 isapplied. L5 (2 bits) provides the number of additional words in theLRD_ID field. LRD_ID an integer number for identifying the first lengthrepair data in (6 + 8 * L5 bits) the FEC repair packet. It starts with 0and is incremented by 1 with each length repair data in its associatedlength repair data block. It only presents when length repair datapresents in the FEC repair packet. i.e., I is set to 1.

Note, 1) The order of the fields in the repair FEC payload ID determinesthe order in which source symbols are concatenated in the source symbolblock.

2) For a given source flow, the order of the SS_start_seq_nr[i], L[i],and SSB_length[i] fields are determined by the order of packet_ids inthe independent repair FEC payload ID of a repair FEC packet for thesource flow.

3) If the field M indicates that this repair packet carries dependentrepair FEC payload ID, then C and W fields are reserved.

4) If the field M indicates that this repair packet carries dependentrepair FEC payload ID, then ssbg_mode, # of packet_id, list_packet_id,CP, PWT and RS_length fields shall not be present.

FIGS. 18 and 19 are views illustrating repair packet blocks fortransmitting repair symbols generated by applying FEC to source packetblock according to an embodiment of the present disclosure. Theindependent repair FEC payload ID is transmitted in the first, third,and fifth repair packets, and the dependent repair FEC payload ID istransmitted in the second and fourth repair packets. The receiver may beaware of the order and list of the Packet_ID's included in thecorresponding source flow from the independent repair FEC payload ID andmay also obtain the FEC configuration information required for FECoperation. Although not shown, the dependent repair FEC payload ID mayinclude only the location information in the repair symbol block of therepair symbol present in the repair packet received along with therepair FEC payload ID information specified in w13982, or in the MMTPpacket header, it may be replaced using the packet sequence numberfield. In this case, the dependent repair FEC payload ID is not presentas shown in FIG. 19.

According to an embodiment of the present disclosure, higher-qualityservices may be offered to the user. According to the presentdisclosure, the receiving device may differentiate each data stream fromseparate control information different from the source packet or streamdifferentiating information in the FEC packet, grasp the repair streamgenerated for FEC protection on each data stream, smoothly perform FECdecoding, and generate a repair flow for a predetermined number of datastreams included in the generated source packet flow without influencingthe source packet.

Although specific embodiments of the present disclosure have beendescribed above, various changes may be made thereto without departingfrom the scope of the present disclosure. Thus, the scope of the presentdisclosure should not be limited to the above-described embodiments, andshould rather be defined by the following claims and equivalents thereof

What is claimed is:
 1. An apparatus for receiving a packet in abroadcasting system, the apparatus comprising: a transceiver configuredto: receive the packet including at least one repair symbol, wherein theat least one repair symbol is included in a repair symbol block which isgenerated, by a sending entity, from a source symbol block by forwarderror correction (FEC) encoding, and wherein the source symbol block isgenerated, by the sending entity, based on a mode among a pluralitymodes for generating the source symbol block from a source packet block,and receive a message which includes information indicating the mode;and a controller configured to process the packet and the message,wherein the plurality of modes comprises a first mode in which a paddingis added to a source packet in the source packet block, and a secondmode in which padding is not added to source packets in the sourcepacket block.
 2. The apparatus of claim 1, wherein the packet includesinformation indicating a number of repair symbols included in the repairsymbol block, and information including sequence numbers of the at leastone repair symbol.
 3. The apparatus of claim 1, wherein the packetincludes information indicating a number of source symbols included inthe source symbol block, and information indicating a sequence number ofa first source symbol of the source symbols.
 4. The apparatus of claim1, wherein the packet includes information indicating a timestamp of thepacket.